This research focuses on the central unsolved problem of psychiatric epidemiology, the problem of how to measure psychiatric disorders independently of treatment status in the general population. Its major aim is to test the sensitivity and specificity of the newly developed Psychiatric Epidemiology Research Interview (PERI) as a first-stage instrument to screen functional psychiatric disorders among adults in a demographically complex urban population. To this end, we are investigating PERI's relationship to other potential screening instruments in a sample of 600 adults from the general population and calibrating PERI on a sample of 500 psychiatric patients with DSM-III diagnoses of schizophrenia and the schizophreniform psychoses, affective disorders, various types of disorder under the heading of neurosis, anti-social personality, alcohol abuse, and drug abuse. The research setting is Washington Heights, a section of Manhattan in New York City that surrounds Columbia Presbyterian Medical Center. It is a demographically complex urban area containing large percentages of blacks and Puerto Ricans as well as members of more advantaged ethnic groups. The results should provide a major step toward the development and testing of a two-stage procedure for case identification and classification. The findings should also be important for needs assessment and for the planning and evaluation of mental health services in Washington Heights.